I don't have the level of experience in multiple installs that you have. I am most familiar with the laser Interceptor, than with blinders or others. The Laser Interceptor can be mounted vertically and works as well as mounting horizontally according to multiple user radardetectors.net.
Mine are mounted vertically in the grill. It has been tested against multiple types of radar guns with JTG results. I have only had two real life hits both successful.
As for mounting under the bumper versus a higher spot in addition to the increased theft risk, you may want to think if most of the laser traps are when you are cresting a hill versus from an overhead. When cresting a hill reflective parts will be visible before the jammers have line of sight to the gun.